How Screen Mirroring Works

Imagine displaying the contents of your smartphone, tablet or PC onto the big screen with just a few simple steps. You might’ve heard about screen mirroring, streaming and casting, but there are subtle differences between each of these terms. In this detailed article, we’ll get to know why screen mirroring is a great solution for classrooms and meeting rooms as well as the differences between screen mirroring and media streaming.

At the heart of it, both screen mirroring and media streaming refer to sharing content to a projector or TV from a compatible device, be it a smartphone, laptop, PC or tablet. The difference between screen mirroring and media streaming is often overlooked. We get this question a lot and want to clear up the confusion between the two types of technology.

Highlights

The difference between screen mirroring and media streaming lies in the way the content is being transmitted or displayed on the big screen.

Screen mirroring involves sending what’s on your computer screen to a TV or projector via a cable or wireless connection.

Casting is another word for media streaming but is a branded term used in reference to Google Chromecast.

Screen mirroring and streaming

Like we mentioned before, the major difference between screen mirroring and media streaming is the way in which the content is shared to the display. In screen mirroring, as the name rightfully suggests, you mirror the contents of a source device onto your display. Whatever appears on the device, appears on your display as well. In the case of media streaming, the display receives content via a digital media player. This technology does not duplicate the contents present on the screen of your device.

Screen mirroring technologies

There are several types of technology standards for screen mirroring each with their own histories and pros and cons.

Miracast

Miracast is one of the most widely available technologies for wireless screen mirroring. Miracast is a part of the WiFi Alliance and came out way back in 2012. But the problem with Miracast is that it does not support Apple devices. Devices that do not have the support for Miracast can opt for dongles that come with the technology built in.This makes it very easy to convert older devices that do not have the hardware capabilities to support screen mirroring.

It is important to note that Miracast is not a product, but rather a technology. It implements peer-to-peer WiFi Direct standard and allows streaming of 1080p HD videos as well as 5.1 channel surround sound. As of March 2017, there are only about 6,700 devices that are certified by the WiFi Alliance to support Miracast.

Even though Miracast came out in 2012, there is another widely used standard known as AirPlay, which is from the tech giants at Cupertino, Apple. The reason why Miracast does not support Apple devices is simply due to the fact that Apple does not provide any kind of support for Miracast.

Miracast’s lack of support for Apple devices is a major downside because of that fact that a huge number of Apple devices are present in educational institutions as well as at the workplace. If they need to perform screen mirroring they’ll have to go for a device like Airtame. You can read more on the detailed differences between Airtame and Miracast in our Miracast alternative article.

MHL

MHL stands for Mobile High-Definition Link and it is a specification brought in by a group of companies that includes Samsung, Nokia, Toshiba, and Sony. MHL is one of the best standards for high-quality content and responsiveness. The only downside is that MHL is wired and not wireless.

MHL uses a micro USB port to HDMI converter that can transfer contents from your phone to your TV. Do note that all phones do not support MHL and most of the lower end phones don’t support it either due to a few hardware limitations and cost.

But most of the midrange and flagship smartphones come with support for MHL. Mobile gaming is a very popular application of MHL due to the lag-free experience that it creates. You don’t have to worry about the charge on your smartphone as MHL charges your phone through the micro USB port as well.

DLNA

DLNA which stands for Digital Living Network Alliance is one of the powerful standards for wireless screen mirroring. The only problem is that it was introduced by Sony and it tends to work best with Sony devices like Sony Bravia, Sony PlayStation, Sony Xperia and Sony VAIO.

DLNA operates using a client-server model. What this means is that, when the client and server are connected, the client can access the files present on the server. Simply put, if your PC and TV supports DLNA, you can access the files present in your PC from your TV.

Even though this sounds very convenient and powerful, in practice there are a few complications that arise. DLNA works only with files and you cannot actually send over a browser window or YouTube. There are other restrictions with regards to the format of the file as well as DRM restrictions for streaming certain content.

Screen mirroring

The above figure rightfully depicts what the term screen mirroring means. Screen mirroring involves connecting your device to a common network or to a network hosted by the streaming device to display the exact same content on the display. It can be done with wires or wirelessly.

Wired screen mirroring

The best example for wired screen mirroring is our faithful HDMI cable. HDMI stands for High Definition Multimedia Interface and it transfers information from the connected device to a display digitally (0s and 1s). This whole procedure can be broken down into three steps

1. Detecting a connection

The HDMI port is found on the backside of your PC. Find the rear portion of your graphics card and connect the HDMI cable to the port. After that, connect the opposite side of the cable to your TV. Once you boot up your PC, the graphics card will detect the new display. On a laptop, you can press the Windows button and P to bring about different options to display your laptop screen on your TV.

2. Sharing information

Since there are many different screens and resolutions, your computer needs to know some information before it can start a connection with a second screen. This second step tells your computer what the audio and video settings of your TV are, so your computer can display the information properly. This is also called E.D.I.D. (Extended Display Identification Data).

3. Mirroring starts

The final step is obviously the actual screen mirroring. Once the connection is set up and the settings are identified, the information is sent from the computer to the TV. The TV screen mimics the contents of the computer screen exactly as it is. You can choose to display both screens, one screen only and extend as well.

Wireless screen mirroring

Just as with almost every wired technology, screen mirroring also has a wireless counterpart. Wireless screen mirroring can be achieved using various different technologies like MHL, DLNA, and Miracast. We have already seen how each of these function, but let’s take a look at wireless streaming with HDMI with an example.

Wireless streaming with HDMI

Wireless streaming with HDMI refers to the life mirroring of your PC screen to TV using WiFi. It can also be done for smartphones and tablets as well.

Let us take a look at the Airtame device as an example. Airtame uses a WiFi connection to mirror the contents of your PC or smartphone. The way it works is quite brilliant because it takes screenshots at the rate of 24 images per second. You may be wondering why 24? This is because 24fps is the standard for videos and is an adequate frame rate for detection of realistic motion by the human eye.

Once the screenshots are captured, the computer packages it and sends it over the WiFi connection to the Airtame device that is plugged into the TV or monitor’s HDMI port.

The Airtame device unpacks this information and displays it on the TV. Even though it might sound like a lot of things happening at once, you’ll never notice a lag as everything happens in real-time. The capturing of screenshots, packing, transmission over WiFi, unpacking and displaying on the TV, takes place effortlessly and almost like magic.

Media streaming/casting

Media streaming refers to receiving online content from a streaming device to a TV.By now, there are several media players out on the market from Apple TV to Roku to the Amazon Firestick. A popular example of a media streaming device is the Google Chromecast. It is a digital media player that is capable of playing online content on your TV. This differs from wireless streaming with HDMI in the fact that it doesn’t mirror the contents of your PC or smartphone but actually gets content from the internet.

So what does Chromecast actually do? It downloads content from the Internet to your television on the fly. Media streaming is quite predictable in nature when considering the fact that there are no mouse movements and operations performed haphazardly. Due to this very reason, media streaming has a much better latency compared to screen mirroring.

This is also the reason why media players can offer better encoding and compression. The difference is felt while watching a movie using screen mirroring and watching a movie using a media streaming device. The mirrored screen may lag or show inconsistencies while the streaming device will give a better output.

Chromecast shouldn’t be confused with Miracast and they’re actually quite different from each other even though the results might seem quite similar. Miracast creates a direct peer-to-peer connection between two devices while Chromecast connects to a device using your local network.

The Chromecast device is like a small computer that can connect to a network and stream content using a highly modified version of the Chrome browser. You need to install the Google Cast app on your smartphone to connect to the Chromecast dongle, but the connection and pairing take place in a jiffy. YouTube and Netflix work flawlessly with Chromecast.

The great thing about it is that you can continue using your phone while the media is being streamed. This is because your phone is not doing any of the hard work, the tiny little dongle takes care of all that. While using YouTube, your phone simply passes the URL info to Chromecast, while Chromecast takes care of the rest of it.

Chromecast now offers both Desktop casting and Tab casting for apps that don’t support Chromecast natively. Tab casting does consume quite a bit of memory while in use and this might affect performance if you are using an older device. Chromecast is a media streaming device at heart, so the screen mirroring capabilities are not top-notch. It does suffer from latency issues, but again, this wouldn’t be a problem for a person using it at home.

Note: We’ve had some feedback about our Chromecast alternative article. Some have stated that Chromecast does offer screen mirroring from a computer. Chromecast does offer support for screen mirroring but is directed more towards the home user. Airtame on the other hand is a professional solution that offers an integrated ecosystem of services that cater to schools and businesses.

Advantages of wireless screen mirroring vs streaming/casting

The biggest and most obvious advantage of screen mirroring over streaming is the ease with which the user can control what they share on the big screen. While media streaming is geared more towards entertainment purposes, screen mirroring allows for more professional use cases than with media streaming.

At the end of the day, what device you choose depends on your usage patterns. If you are someone who loves your movies and shows, it is a no-brainer to go for a media player like the Chromecast. It offers flawless performance with YouTube, Netflix, and other streaming apps. Their mirroring capabilities are not yet in full swing.

However, if your main use case is to showcase presentations, create engaging discussions and effortlessly switch between various computer platforms in an office or school, screen mirroring technology like Airtame is the way to go.

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